The present invention deals with a user input device. More particularly, the present invention deals with a user input device having inclination sensors disposed thereon to detect inclination of the user input device.
Many different types of user input devices are currently used for providing user input information to a computer. Such user input devices can include, for example, a point and click device (which is referred to as a computer mouse), a keyboard, joystick, and a track ball. Such user input devices all typically sense the movement of a movable element relative to a fixed base or housing portion and provide the computer with an input signal indicative of that relative movement.
Recently, however, free-space type user input devices have been introduced. Such devices use gravity-sensing accelerometers to sense inclination of the user input device, in free space, relative to a gravity vector. Where a plurality of such sensors are provided, the sensors sense inclination of the user input device about a plurality of inclination axes. Such information is provided to a computer to control a cursor, a player, or a vehicle inside of a computer application or simulation, for example.
In conventional free-space type input devices, a pair of accelerometers are fabricated on a single silicon substrate and are mounted onto a single package. The accelerometers have sensing axes which are directed orthogonally to one another. Such typical devices, it is believed, have the accelerometers mounted within the user input device such that the orthogonal accelerometer sensing axes are aligned with the primary axes of expected rotation or inclination of the user input device. For example, in one embodiment, one of the sensing axes of the accelerometers is aligned with the pitch axis of the user input device, while the orthogonally mounted sensing axis is aligned with the roll axis of the user input device. This has led to a number of different problems.
Because the two sensing axes are mounted in a fixed orthogonal relationship, the output from the accelerometers can never exceed a total of 90 degrees of sensed inclination. In other words, as one of the sensing axes is being tilted in an active direction (i.e., such that the sensing axis can sense inclination in that direction), the other sensing axis is being tilted toward a non-active inclination angle. Thus, the sum of the output of the two accelerometers can never exceed 90 degrees. Therefore, the range of inclination angles which can be sensed by conventional devices is quite narrow.
In addition, the output of conventional accelerometers is non-linear for most angles. The output is generally sinusoidal. Thus, the sensor can be slightly too sensitive to motions around a center point, yet largely insensitive to motions at the edges of the range of angles which can be sensed.